1. Field of the Invention
The present invention relates generally to advances in medical systems and procedures for prolonging and improving human life. More particularly, this invention relates to a method and apparatus for thermally treating the intervertebral disc to relieve pain associated with abnormalities of the disc due to pathology of the disc or interruption of the various neural processes in and around the disc.
2. Description of the Related Art
The use of radiofrequency electrodes for ablation of tissue in the body or for the treatment of pain is known. In a typical application, a radiofrequency probe or a resistive heating probe may be constructed in an elongated, cylindrical configuration and inserted into the body to a target tissue which is to be treated or ablated. In the case of a radiofrequency probe, there may be an exposed conductive tip portion and an insulated portion of the probe. When connected to an external source of radiofrequency power, heating of tissue occurs near the exposed conductive portion of the probe, whereby therapeutic changes in the target tissue near the conductive tip are created by the elevation of temperature of the tissue. Thermal probes can also be made by resistive heating of a portion of the probe so as to heat surrounding tissue by thermal conduction. By reference, the products of Radionics, Inc., located in Burlington, Mass., include commercially available radiofrequency generators and electrode systems of varied configurations. A paper by Cosman, et al, entitled “Theoretical Aspects of Radiofrequency Lesions in the Dorsal Root Entry Zone”, Neurosurgery, December 1984, Vol. 15, No. 6, pp. 945-950, describes aspects of tissue heating using radiofrequency electrodes and probes.
The use of thermal therapy in and around the spinal column is also known. Heating of an intervertebral disc to relieve pain is described in commonly assigned U.S. Pat. No. 5,433,739 entitled “Method and Apparatus for Heating an Intervertebral Disc for Relief of Back Pain” and in commonly assigned U.S. Pat. No. 5,571,147 entitled “Thermal Dennervation of an Intervertebral Disc for Relief of Back Pain”, the contents of each patent being incorporated herein by reference. In these patents, electrodes are described for either radiofrequency or resistive thermal heating of all or a portion of the intervertebral disc. Straight, curved, and flexible-tipped electrodes are described for this purpose.
U.S. Pat. No. 6,007,570 to Sharkey/Oratec Interventions discloses an intervertebral disc apparatus for treatment of the disc. The apparatus includes a catheter having a self-navigating intradiscal section in the form of a conventional helical coil. In use, the intradiscal section is advanced through the nucleus pulposus and is manipulated to navigate within the nucleus along the inner wall of the annulus fibrosis. An energy delivering member incorporated into the apparatus adjacent the intradiscal section supplies energy to treat the disc area.
The apparatus disclosed in Sharkey '570 is subject to several disadvantages which detract from its usefulness in relieving pain associated with an intervertebral disc. For example, navigation of the helical coil of the catheter within the nucleus pulposus requires the support structure to wrap around in an approximately circular fashion from the anterior portion to the posterior portion of the intervertebral disc. This serpentinus path of the support structure is difficult for the surgeon to effectuate. Moreover, the configuration of the helical support structure increases the risk of probe kinking and is deficient in consistently facilitating the prescribed movement within the disc.
It is desirable to treat the posterior or posterior/lateral portion of the intervertebral disc for the indication of mechanical degeneration of the disc and discogenic back pain. Pain can be derived from degeneration or compression of the intervertebral disc in its posterior or posterior/lateral portions. There is some innervation of the intervertebral disc near the surface of the disc and also within its outer portion known as the annulus fibrosis. Mechanical damage such as fissures or cracks within the disc caused by age or mechanical trauma may result in disc innervation which is believed to be associated with painful symptoms.
Accordingly, the present invention is directed to a novel apparatus and method of use which provides for direct and confirmable placement of a thermal or electromagnetic field (EMF) treating element within the posterior/lateral and posterior portions of an intervertebral disc for thermal treatment. The apparatus includes a percutaneously introducable thermal application device having a novel configuration which provides excellent torque transmission and an increased flexure in a specific direction thereby facilitating the advancement of the thermal device within an intervertebral disc and preferably, for example, in the annulus fibrosus between layers of annular tissue.